The present invention relates in general to aircraft, and in particular, to lightweight, portable aircraft having improved flight, safety, and construction characteristics. More specifically, this invention relates to an improved aircraft including a primary, arc-shaped lifting airfoil in combination with a secondary stabilizing airfoil assembly, both supported and fixed relative to each other by a tubular fuselage assembly.
The airfoil assemblies are constructed of a fabric or like skin material tensioned over an adjustable wing frame and utilize the dynamic forces of the air during flight to bias stretch the wing skin into the desired wrinkle-free airfoil configuration.
The invention herein disclosed provides an adjustable, lightweight, tensioned fabric structure which forms a near zero thickness, single surface airfoil having increased strength, high lift potential and superior aerodynamic properties.
Numerous different configurations of lightweight, low speed aircraft have been proposed in the prior art, but these designs have failed to obtain optimum flight and safety characteristics.
Typically, prior art devices have utilized traditional wing airfoil shapes to supply the aerodynamic lift necessary for sustained flight. Such prior craft have employed expensive, complex, and often dangerously fragile construction and design techniques in order to obtain light weight. In addition, known techniques have often required substantial expenditures of time and effort to assemble and disassemble them, and yet have not always provided a sturdy, lightweight aircraft capable of effective operation.
To overcome these shortcomings, some prior art aircraft have had to sacrifice desirable flight capabilities and characteristics in order to achieve the objective of low weight and/or economy. Such designs, in reducing weight at the expense of performance and strength, have, of necessity, compromised the overall safety of the aircraft in addition to its ruggedness and simplicity of design.
The present invention, however, due to its innovative design, and methods of contruction, makes it possible to construct a ligthweight and inexpensive aircraft, overcoming the deficiencies present in most prior art devices. Not only is the structure of simple construction, minimizing maintenance and expense, but it is also inherently safe and rugged as well. The arc-shaped, fabric tension, wing design provides great overall wing strength in addition to inherent pitch and spiral stability without deleterious wing-fuselage joints present in conventional foil designs. Substantial wing end plate effects, stall stability and resistance to downward wing loading, most often applied by wing gusts or currents, are also properties inherent in this design, but typically unfound in the prior air for an aircraft of comparable weight and simplicity.
The aircraft of the invention attains aerodynamic efficiency far superior to other similar devices previously disclosed. The arc-like configuration of the invention utilizes a relatively short wing span, requiring minimal storage and transportation area, while offering high lift and minimizing aerodynamic drag and other deleterious properties present in more traditional wing designs. An example of an arc-like configuration of the prior art not capable of the improved results of the invention is disclosed in U.S. Pat. No. 3,572,614 issued to William R. Bertelsen on March 30, 1971.